From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from outbound.qs.icloud.com (qs-2006f-snip4-3.eps.apple.com [57.103.85.184]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A24E02BE7BE for ; Mon, 20 Jul 2026 05:08:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=57.103.85.184 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784524109; cv=none; b=loqc7a92xMICSJ+IXLv/e7x6CJF8oZ9asZ2E8rDV1YEGW8GFsDGglcJByjDVhWZDOMxAE3UPATQ1Ts6KUQ0d7NEYX1G65orhmGt8c626XdgxUiQsYThN1S2EJOekvElZGOca111+e+O6zGTyk/SpoQfCI58wOdTT4X86XdnpdVw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784524109; c=relaxed/simple; bh=vRfWGSnXj1NRnsdshI2zRjQUulhC/QjmbpiKDROQvIQ=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=Swlv+hvZeXo/2+SzJsWPWIa2gKFwhX9LYT4QMGB8MVEjqKrBjxzNzxnn0CMwsDRNMZTBxHBVaey6FWbzV3vuwf3yZSz5kX7qx7I+8dC78a1HOwK0Og8gC23Cu71KaBcm1jFuBv4cAbslXsLo4czTi8zN3b2hIOXUHJxsqriKaL0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=icloud.com; spf=pass smtp.mailfrom=icloud.com; dkim=pass (2048-bit key) header.d=icloud.com header.i=@icloud.com header.b=pUdKd/7d; arc=none smtp.client-ip=57.103.85.184 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=icloud.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=icloud.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=icloud.com header.i=@icloud.com header.b="pUdKd/7d" Received: from outbound.qs.icloud.com (unknown [127.0.0.2]) by p00-icloudmta-asmtp-us-east-2d-60-percent-7 (Postfix) with ESMTPS id CA171180013D; Mon, 20 Jul 2026 05:08:23 +0000 (UTC) X-ICL-RepId: 019f7dec-e043-74fb-9e93-c65bb5ca77ab X-ICL-Out-Info: HUtFAUMEWwJACUgBTUQeDx5WFlZNRAJCTQhMHVwGXRxCCkEdXgBLVxQEAlodRw5AHVYWWAhOK1sTVRdGCRkIXR0ZHldQXgheH0wcHQ5YBhICWkUBXRcDVxxWRVwYQwldBVccHRxERVsTVRdGCRkIXR0ZCEcfCjADQg5WA0MHRQAtGRxXUF4IXh9MHB0OWAYSHVAcDlEFWwBGCU8BXRoJUwRaEB4ZWwkfFlUNQAUaHQddDFVXDw5fAREJHAMJAQlyGVoUXBhTRVEfVEYTGU4bV01QG18CQg8= Dkim-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=icloud.com; s=1a1hai; t=1784524106; x=1787116106; bh=p5HyYFMk+G/YKnBn8V0qp4YenxBWpgT+6vv4nWfMrPQ=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:To:x-icloud-hme; b=pUdKd/7dRm/6yP4H6XvLXbgOKm9ud6pR7M/zuwXdYHFmheJkAtI80umHQAJFeiQWRoG7yOjoK/Dbfv/amK/oJz3IJWANDVkDjUD4GC2w6RDu5rY57wKKBtUE0cagorvn/PX+ls+T5U9P1zGqnK8UF0y7CYSNb8+gAKj30gT1upYolOgdmLvItQqDoRRo956YDAOSHn9WQe/0lO5kHQYHZKnsVUrJ3u7YX1yW6Z8k+xN+NA+nd+I26wCcougb7AZMaTIcoxS4aS7j2HPsCBHfQUNvuIheMuongNEiwyBfGUFlPvt5IC3QkIyrJomIR+ZeqeoWCFn1n7Bmi84SgZXVNA== Received: from [21.6.122.162] (unknown [17.57.155.37]) by p00-icloudmta-asmtp-us-east-2d-60-percent-7 (Postfix) with ESMTPSA id 5E84E180012E; Mon, 20 Jul 2026 05:08:16 +0000 (UTC) From: Zhang Peng Date: Mon, 20 Jul 2026 13:07:42 +0800 Subject: [PATCH v5 5/5] mm/vmscan: flush TLB for every 31 folios evictions Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260720-batch-tlb-flush-v5-5-db943a0d0d6b@icloud.com> References: <20260720-batch-tlb-flush-v5-0-db943a0d0d6b@icloud.com> In-Reply-To: <20260720-batch-tlb-flush-v5-0-db943a0d0d6b@icloud.com> To: Andrew Morton , David Hildenbrand , Lorenzo Stoakes , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Johannes Weiner , Shakeel Butt , Axel Rasmussen , Yuanchu Xie , Wei Xu , Michal Hocko , Qi Zheng , "Liam R. Howlett" , Qi Zheng Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Barry Song , Kairui Song , Zhang Peng X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1784524064; l=5688; i=zippermonkey@icloud.com; s=20260309; h=from:subject:message-id; bh=vRfWGSnXj1NRnsdshI2zRjQUulhC/QjmbpiKDROQvIQ=; b=EvGUlVN4y70BkfYRM2zX0HE1C0Yr+zYubCcxUThrRzZh/56vO9L1FCC5cpqFHfSBKXSks/K6x ab87sJ8slkXC8FC71/vMjQO1RI+QwEvN7iw8I9vdFs7xRGYx+2jvU/A X-Developer-Key: i=zippermonkey@icloud.com; a=ed25519; pk=tPCLpFnBfIyHsp0k7eaUTUREEa36bQNW/69X+NS8wBU= X-Proofpoint-ORIG-GUID: NROdlRa12C_BqvsJFnYbjXxtk8lK5x-b X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzIwMDA1NCBTYWx0ZWRfX9Qxm5rjC/Y+/ Nyqv2bSDk/Ad1hz66wVCz5lEFOdq1ruTvxVh8zXnAitzw8Lioa4ihJjdbfn9toUKidIR8+jXm1T PYfDTm1JbV7+Bt7WNkH9dFnpHYsXTmjiV8Oc/ZQrpnVI6IqdHFN+MBbMi5LZRiEsSp2nzVLbGRF 5M7za2BW9HVDq/ecRgMVspYC/kvC2wRn67QlDRz3cUced4gnl6mqPOja5Xck3rXtAaZINeFpdFP C86P+xbvl3aaVLJ8GQL812k2UPb6Sx5DA79KlMWXKCqYiqYZWpaioaajzr5eOin97XWGzet02KK 9tcZL8xbjj1Mu0wWWRi X-Proofpoint-GUID: NROdlRa12C_BqvsJFnYbjXxtk8lK5x-b Currently we flush TLB for every dirty folio, which is a bottleneck for systems with many cores as this causes heavy IPI usage. So instead, batch the folios, and flush once for every 31 folios (one folio_batch). These folios will be held in a folio_batch with their lock released, then when the folio_batch is full, do the following steps: - For each folio: trylock - recheck still evictable (writeback, mapped, dma_pinned). If no longer evictable, put back via ret_folios. - Flush TLB once for the whole batch. - Pageout each survivor via folio_try_pageout(). The recheck step is required because dropping the folio lock between shrink_folio_list() and pageout_batch() opens a window in which a parallel swapin (do_swap_page) can fully complete and install a new PTE; once mapped, a parallel GUP can pin the folio without taking the folio lock. Folios caught by any of these checks are put back via ret_folios. Suggested-by: Kairui Song Signed-off-by: Zhang Peng --- mm/vmscan.c | 92 +++++++++++++++++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 84 insertions(+), 8 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index bb479ead1ee0..251535613336 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1220,6 +1220,71 @@ static bool folio_try_pageout(struct folio *folio, return false; } +static void pageout_batch(struct folio_batch *fbatch, + struct list_head *ret_folios, + struct folio_batch *free_folios, + struct scan_control *sc, struct reclaim_stat *stat, + struct swap_iocb **plug, struct list_head *folio_list, + unsigned int *nr_reclaimed) +{ + int i, nr = folio_batch_count(fbatch); + int count = 0; + struct folio *folios[FOLIO_BATCH_SIZE]; + + /* + * Collect survivors into a local array: this avoids walking and + * mutating @fbatch in the same loop, so its invariant (only + * folios[0..nr) are valid) is preserved throughout. + */ + for (i = 0; i < nr; i++) { + struct folio *folio = fbatch->folios[i]; + + if (!folio_trylock(folio)) { + list_add(&folio->lru, ret_folios); + continue; + } + + VM_WARN_ON_FOLIO(folio_test_lru(folio), folio); + + /* + * Recheck what shrink_folio_list() verified before dropping + * the folio lock. Between that folio_unlock() and our + * folio_trylock() here, a parallel swapin (do_swap_page) can + * fully complete -- taking the lock, installing a new PTE, + * and releasing the lock -- after which a parallel GUP + * (O_DIRECT, vmsplice, RDMA, ...) can pin the folio through + * that PTE without taking the folio lock. Each flag catches + * one case: + * folio_test_writeback -- defensive guard. + * folio_mapped -- swapin installed a PTE. + * folio_maybe_dma_pinned -- GUP pinned through such a PTE. + */ + if (folio_test_writeback(folio) || folio_mapped(folio) || + folio_maybe_dma_pinned(folio)) { + folio_unlock(folio); + list_add(&folio->lru, ret_folios); + continue; + } + + folios[count++] = folio; /* keep lock held */ + } + folio_batch_reinit(fbatch); + + if (!count) + return; + + /* One TLB flush for the whole batch */ + try_to_unmap_flush_dirty(); + + for (i = 0; i < count; i++) { + struct folio *folio = folios[i]; + + if (!folio_try_pageout(folio, free_folios, sc, stat, plug, + folio_list, nr_reclaimed)) + list_add(&folio->lru, ret_folios); + } +} + static bool folio_try_unmap(struct folio *folio, struct reclaim_stat *stat, unsigned int nr_pages) { @@ -1261,6 +1326,7 @@ static unsigned int shrink_folio_list(struct list_head *folio_list, struct mem_cgroup *memcg) { struct folio_batch free_folios; + struct folio_batch flush_folios; LIST_HEAD(ret_folios); LIST_HEAD(demote_folios); unsigned int nr_reclaimed = 0, nr_demoted = 0; @@ -1269,6 +1335,7 @@ static unsigned int shrink_folio_list(struct list_head *folio_list, struct swap_iocb *plug = NULL; folio_batch_init(&free_folios); + folio_batch_init(&flush_folios); memset(stat, 0, sizeof(*stat)); cond_resched(); do_demote_pass = can_demote(pgdat->node_id, sc, memcg); @@ -1564,15 +1631,18 @@ static unsigned int shrink_folio_list(struct list_head *folio_list, if (!sc->may_writepage) goto keep_locked; /* - * Folio is dirty. Flush the TLB if a writable entry - * potentially exists to avoid CPU writes after I/O - * starts and then write it out here. + * Drop the lock so swap faults finding this folio + * via swap cache lookup can make progress; the + * recheck that this necessitates is documented in + * pageout_batch(). */ - try_to_unmap_flush_dirty(); - if (!folio_try_pageout(folio, &free_folios, sc, stat, - &plug, folio_list, &nr_reclaimed)) - goto keep; - continue; + folio_unlock(folio); + if (!folio_batch_add(&flush_folios, folio)) + pageout_batch(&flush_folios, + &ret_folios, &free_folios, + sc, stat, &plug, + folio_list, &nr_reclaimed); + goto next; } if (!folio_try_reclaim_free(folio, &free_folios, sc, stat, @@ -1597,6 +1667,12 @@ static unsigned int shrink_folio_list(struct list_head *folio_list, list_add(&folio->lru, &ret_folios); VM_BUG_ON_FOLIO(folio_test_lru(folio) || folio_test_unevictable(folio), folio); +next: + continue; + } + if (folio_batch_count(&flush_folios)) { + pageout_batch(&flush_folios, &ret_folios, &free_folios, sc, + stat, &plug, folio_list, &nr_reclaimed); } /* 'folio_list' is always empty here */ -- 2.43.7